Scapho-lunate dissociation is the most common carpal instability. Scapho-lunate dissociation can be characterized by diastasis between the scaphoid and lunate bones and rotatory subluxation of the scaphoid. Scapho-lunate dissociation typically causes wrist pain, swelling, clicking, progressive radiocarpal arthritis, and decreased motion and grip strength. There are currently many surgical treatment options that may be indicated depending on a variety of factors, including healing potential of the ligament, time elapsed since injury, alignment/reducibility of the carpal row and presence/extent of degenerative changes in the wrist. However, all of these treatments have some undesirable results (e.g., loss of range of motion, long periods of immobilization and/or high rates of failure). With the exception of the bone-tissue-bone grafts, each of the treatment options mentioned below have been used for over 10 years. Additionally, the bone-tissue-bone grafts and the RASL procedure discussed below have only limited clinical results.
One method used to treat scapho-lunate dissociation is dorsal capsulodesis. Dorsal capsulodesis can be performed with or without repair of the scapholunate interosseous ligament (SLIL). During either method, a physician temporarily pins Kirschner wires across the scapholunate and scaphocapitate intervals to restore proper carpal alignment during healing. Currently available results indicate that dorsal capsulodesis is associated with long term weakening and provides only limited motion recovery.
Bone-tissue-bone grafts are another treatment option for scapho-lunate dissociation. During the bone-tissue-bone graft procedure, the physician utilizes an autologous bone-tissue-bone graft to replace the scapholunate interval. Complications associated with bone-tissue-bone grafts include the problems associated with a second surgical site and selecting a graft that operates similarly to the SLIL being replaced. As stated above, the results of these treatments are variable and long term outcomes are unknown.
One of the newer and less invasive methods for treating Scapho-lunate dissociation is known as the Reduction and Association of the Scaphoid and Lunate (RASL) procedure. Although long-term results are unavailable, the RASL procedure offers only limited motion recovery and relatively high potential for failure. During failure, screws inserted into the bone during the procedure may back out and protrude into the scapho-lunate interval. In addition, the screws wear and weaken the bone as the bone rotates about the screw during motion. Once a RASL procedure fails the patient is left with very limited treatment options because the damage to the bone is typically very severe.
Chronic instances of scapholunate instability extending towards degenerative arthritis typically require more extreme surgical procedures with highly compromising results. One such option is intercarpal fusion. During the intercarpal fusion procedure, a physician fuses two or more carpal bones (e.g., scapholunate, scaphoid-trapezium-trapezoid, scaphoid-capitate-lunate, and lunate-capitate-triquetrum-hamate) together. As one would expect, fusion of the bones greatly reduces the patient's range of motion. Additionally, there are high complication and failure rates associated with the intercarpal fusion procedure.
Suture anchors are well-known in the prior art and are commonly used by physicians to secure soft tissue to bone. A suture anchor typically includes a body portion and at least one suture secured to the body portion. The body portion is driven into the bone, and a securing means secures the body portion within the bone. For example, many suture anchors have threads, screws, hooks, or deployable members located on the body portion.
In practice, a physician typically drills a hole into a bone. The physician then inserts (e.g., screws, threads, etc.) the body portion of a suture anchor into the bone tunnel. The suture(s) is then secured to the soft tissue (e.g. ligament) using any of a number of methods (e.g., knotting, tying, looping, etc.), depending on the design of the suture anchor being used. Because a suture anchor includes a suture attached to the body portion, the suture anchor secures the ligament to the bone.